Compact camera modules have become ubiquitous and are used in a wide range of applications ranging from consumer electronics, most notably smartphones, to medical systems, such as endoscopes, and automotive safety, e.g., back-up cameras and blind-spot detection. This development is a result of advances in camera manufacturing facilitating significant size and cost reduction. A key technology is wafer-level manufacturing of both lenses and image sensors. In the case of wafer-level lens manufacturing, a very large number of microlenses are molded on a single wafer, which is subsequently diced to produce individual lens modules. Since all the microlenses are molded in a single operation, significant cost savings result from forming a large number of microlenses on the same wafer. In one example, thousands of microlenses are molded on one side of the wafer in a single molding operation. A corresponding set of microlenses may be molded on the opposite side of the wafer in another single molding operation. The wafer is diced, optionally after bonding to one or more other lens wafers, to produce imaging objectives for use in compact camera modules. Wafer-level lens manufacturing is particularly well-suited for the production of microlenses and is, at least in terms of cost, generally superior to conventional single-lens casting.
In conventional wafer-level lens manufacturing, lens resin is deposited between a wafer substrate and a mold. The mold has both lens-shaped recesses for forming microlenses, and overflow recesses for accommodating excess lens resin. The overflow recesses are spaced apart from the lens-shaped recesses by a small distance. When the resin is cured, each microlens on the wafer is surrounded by a ring of cured excess lens resin, known in the art as “yard”. This yard is spaced apart from the microlens by a short distance. Subsequently, when the lens wafer is diced, each lens module formed therefrom includes one or more of the microlenses as well as the yard surrounding each of these microlenses.